Not that long ago, the idea of outdoor “no smoking” zones seemed silly. But when many cities (including New York) banned indoor smoking, smokers began clustering at building entrances, generating tobacco clouds and butt piles. In other words, the indoor bans only moved the problem of second-hand smoke outside. The solution outside many buildings has been to post no smoking signs, like the one above. And while it seems to have forced many smokers to find another perch, or least get a little more exercise before enjoying a puff, the signs clearly don’t always work.